An absorption refrigeration system of the type which uses water and aqueous lithium bromide is disclosed in Japanese Published Unexamined Patent Application No. 58-40468, for example. This system consists chiefly of an evaporator, an absorber, a regenerator, and a condenser. In the evaporator, a chill carrier fluid is deprived of its heat and cooled by the evaporation of water (refrigerant). The water vapor from the evaporator is absorbed into an aqueous solution of lithium bromide (absorbent) in the absorber with attendant heat generation. In the regenerator, the diluted absorbent received thereinto from the absorber through a heat exchanger is heated by a heating fluid, whereby the water is evaporated from the absorbent. The concentrated absorbent thus obtained through the regeneration process is returned via aforeasaid heat exchanger to the absorber, in which it is reused for water vapor absorption. In the condenser there are provided heat transfer tubes through which a cooling fluid flows, so that the water vapor introduced from the regenerator into the condenser will become condensed as it goes into contact with heat conduction surfaces of the tubes.
In the above prior-art system, since the condensation of the water vapor produced in the regenerator is carried out in the condenser indirectly through the heat transfer tubes, it is necessary, in order to increase the rate of condensation, to make the temperature of the cooling fluid considerably lower than the condensation temperature of the water vapor and to provide a large heat conduction area as by using a large number of heat transfer tubes. As a result, the prior-art system has a disadvantage that an external system to be connected to the condenser is limited to one capable of generating a low-temperature cooling fluid, otherwise it being necessary to redesign the entire refrigeration system on a case-by-case basis so as to adapt it to the external system. Another difficulty is that since the condenser must provide a large heat conduction area, the cost of the overall refrigeration system becomes inevitably high.